Twins confusion

Women are the greatest assets in this world. A woman feels extreme happy and proud at the moment when she yield a child. If those kids are twins, then there is no limit to feel happy. My neighbors are also twins who were now at the age of 5. First kid’s is name Arif Jan and the second kid’s name is Asif Jan. Both of them look similar and it is very difficult to differentiate them except their mom Sarah. She used to play a unique game with her servant every day with a bet of $2. She asked her servant to identify who is Arif and who is Asif. Most of the times, servant would wrongly identify them. But sometimes he identifies them correctly at that time she lie to him that he was wrongly identified again. Even though it is a simple game, it is more enjoyable game.